Gary Arthur

My Feedback: (29)

I have a Wren 44 Gold. The idle rpm fluctuates from 60 - 80,000. Sometimes it goes below this and when it tries to regain the idle rpm, it spits out flames.

This is a 44 gold running on 3s lipo. It has the resirictor after the pump (Wren supplied).

I have tried de-gausing the rpm sensor.
I have tried removing the restrictor.
I have tried a restrictor between the inlet and outlet of pump (trying to run in a higher PW range).
I have tried increaseing the decell delay.
I have tried increasing the stability delay.

Same results.

Wren Turbines USA

My Feedback: (39)

Gary,

What fuel pump are you using?

Ron

Gary Arthur

My Feedback: (29)

This one.

Jim Cattanach

All the Wren golds I have seen run on two cell lipos, not three. Would that make a difference?

ron Sweeney

Hi Garry, I have been discussing this very problem on another thread and have been given various pieces of good advice. Although my engine has very low hours it is out of its' warranty period.
My problem started with the engine quitting on landing approach and I thought I had solved the problem by increasing the deceloration ramp to a value of 35. This unfortunately left the turbine idling at about 70k to 80k. A further flame out was enough to tell me that I hadn't solved the problem and was risking my plane by messing any further.
My turbine was supplied with the same pump as yours and I have been advised by two separate sources that the pump may be the problem. I am no expert but am told that the capacity of this pump (too big) leaves it struggling to provide a reliable flow at the 44 gold idle speed. When I access the data after a flame out the default is 'low speed'. I have tried raising the stop speed value to no avail. Tomorrow I am going to order the flight works 100c pump which is designed to suit the smaller turbines. If Wren have this in stock I will fit it and let you know the results.
I am told that a by pass line can be added with a regulated return to the fuel tank can be successful by increasing the fuel flow from the pump but this would be difficult to install in my model which is the tiny Vortex 32 conversion. I will be interested to hear Ron's comments . Ron Sweeney.

Wren Turbines USA

My Feedback: (39)

What I am going to do is forward this to Mike and Gavin for their input. You will have to change the start parameters using the FW pump...but the idle will improve.

I'll be back to you on Tuesday... as England is on a "bank holiday " today.

Also...I have pm'd you.

Ron

littlepiston

My Feedback: (12)

I had the same problem, it is the pump i used the flightworks pump the first 1 did not work but the second one did. i went though a total of 3 pumps befor i found one that would work. It would die on idle, it would surge on idle and if you so much as touched the pump(Hysul) it would die.The flight works pump did the trick.

Gary Arthur

My Feedback: (29)

I received the FW100 pump and instaled it. The idle is not better and with the original battery, my pulse width goes to max 1008 and I only reach 160,000 rpm. I changed out the battery for a larger 3s pack and can now reach full rpm at a pulse width of 860. The idle is still surging 5 - 7000 rpm and if I raise the throttle, it dies when I return to idle. What next? Oh and the burn pattern looking in the tail looks fine.

littlepiston

My Feedback: (12)

Gary post a picture of your set up

Gary Arthur

My Feedback: (29)

My set up is as simple as can be. I have taken the engine out of the plane and have it on a test stand. short lines, simple metal clunk. Do not even have the valve in place. Cant be much simpler than that.

littlepiston

My Feedback: (12)

no dout, however i would like to see what ecu u are using.

ron Sweeney

Hi, I also bought the flight works pump and after experimenting with the auto start and pump ramp values, achieved a consistent start up and run. I re-taught the ecu just in case. Everything seemed fine but the turbine was unsettled in the low rpm ranges and was reluctant to drop back to 55k idle. After several cycles it seemed to improve a bit so I decided to fly. I am not sure what happened but on the base leg prior to landing I think the turbine stopped again and I stalled in and did some minor damage to the model which is now repaired. It was a very windy day so I couldn't hear the turbine so it looks like I am back to square one. I forgot to do the turbine stop diagnosis and subsequently ran the turbine to check all was well so I lost the data. Don't know where to go from here but I will try again on the next quiet day, Ron.

Gary Arthur

My Feedback: (29)

I think I have it sorted out. I changed to another (new) 3s lipo for the ECU, adjusted the pump ramp, decel delay and stability delay. I then re-taught the ECU by going from idle to full and back slowly numerous times. It now idles about 1000 rpm above set point and is steady with maybe 600 rpm fluctuation. Did about 5 runs. After the start the idle is slightly high but it comes down and settles well. A slam up to full and it hits full rpm with a pulse width of around 754 and then a slam back to idle and it settles back to 59,000 (setting is 58,000) with a pulse width of 163.

ron Sweeney

Hi Ron, et al, Having damaged my model following a suspected flame out subsequent to a pump change from Hausle to flight works, I tenuously test flew my model today after conducting a simulated flight on a ground run. This was after a weeks re-build. After two circuits the engine flamed out trailing a stream of fuel vapour. A successful landing revealed that I had forgotten to take out the fuel bung and had starved the pump. I restarted the turbine and had a successful and uneventful flight so hopefully I have cured my proplem with a change of pump. I did experience a little trouble on fuel ramp but this may be down to fine tuning the pump ramp. Hope this is the end to my difficulties. Ron Sweeney.

ron Sweeney

Another quick up-date, several more trouble free flights so the flightworks pump seems to have done the trick. Ron

Gary Arthur

My Feedback: (29)

An update.

I sent my 44 over the pond to Wren. The ran it with the newest ECU on a 2s lipo and the Hausle pump. It ran like a charm. The new ECU does not have the RJ45 connector, instead it has a servo connection for the data terminal (much easier to run an extension). It also has Aux connections for???. The greatest thing is the idle is rock steady and I can still use the Hausle pump with the auto settings.

When I put the engine back into my plane, I had some fuel issues to sort out but all is fine.

Thanks Mike and Wren.....